High-speed circuit breaker



Sept. 23, 1958 w. SCHMIDT ET AL HIGH-SPEED CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed Sept. 27, 1956 Fig. 2.

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Sept. 23, 1958 w. SCHMIDT ETAL HIGH-SPEED CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Sept. 27, 1956 n 5 n R 0 9 m 0 T h I. c n w .II N r a 7/1; I DI r e I n I l r m I 3 e 0 7 W Y I m B w l w I a r l 7 U w W 6 6 8 u 4 Q 7 W H 3 5 9 AM 9 H 5 4 4 5m 5 u m. u g l W .I O 7 ad 3 F .7 9 g W M. o 8 '3 3 90 7 4 A l 5 i I 8 7 6 ATTORNEY United States Patent 1 2,853,579 HIGH-SPEED CIRCUIT BREAKER Werner Schmidt and Max Proschmann, Berlin-Siemensstadt, Germany, assignors to Siemens-Schuckertwerke Aktiengesellschaft, Erlangen, Germany, a corporation of Germany Application September 27, 1956, Serial No. 612,479 12 Claims. (Cl. 200-106) This invention relates to circuit breakers and more particularly to high-speed operating mechanism for circuit breakers.

In high-speed circuit breakers for interrupting high direct currents it is very important that the contacts start to separate as soon as possible after the breaker is tripped. It is also important that the opening operation be accelerated at least until the contacts are separated to a point most favorable for are extinction. In highspeed circuit breakers which use stored-energy operating means for opening the contacts, the stored-energy means, when released by operation of the breaker trip device, must effect a certain amount of movement before the contact pressure becomes zero and the contacts start to separate. Much higher opening speed can be attained if the contact pressure becomes Zero and the contacts start to open the instant the breaker is tripped.

It is an object of the invention to provide a high-speed circuit breaker in which the contact pressure becomes zero and the contacts start to separate the instant the circuit breaker is tripped.

Another object of the invention is to provide a highspeed circuit breaker embodying stored-energy operating means which provides both contact pressure and the opening force.

Another object of the invention is to provide a highspeed circuit breaker having a stored-energy device which in the closed position of the breaker applies contact pres sure and when released applies a force to open the breaker contacts.

The invention both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description thereof when read in conjunction with the accompanying drawings.

In said drawings:

Figure 1 is a schematic view illustrating the principles of the invention.

Fig. 2 is a vertical sectional view of a circuit breaker embodyiig the principles of the invention, the circuit breaker being shown in the closed position.

Fig. 3 is a vertical sectional view of a portion of the mechanism shown in Fig. 2, but showing the breaker immediately after it has been tripped.

Fig. 4 is a view similar to Fig. 3 but showing the breaker in the fully opened position.

Fig. 5 is a view similar to Fig. 2 but showing the circuit breaker just before the end of a closing operation.

Referring to Fig. 1 of the drawings, the circuit breaker includes spaced stationary contacts 11 and a cooperating movable bridging contact 13 secured to the upper end of a contact operating rod 15. A lever 17 pivotally mounted on the lower end of the rod has a latch end 19 normally engaged by a latch 21 of a trip device 23. The other end 25 of the lever 17 is pivotally connected by means of a pivot 27 to one end of a link 29 which has its other end pivotally supported on a fixed pivot 31. A stored-energy device comprising a spring 33 compressed bet-ween a spring seat 35 at the upper end of the rod 15 and the end 25 of the lever 17 exerts a force upwardly on the rod 15 and downward on the end 25 of the lever 17. The end 25 of the lever 17 is supported by a mass 37 which, in turn, is resiliently supported by a spring 39.

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Since the lever 17 is latched up at 19 in the closed position of the breaker, the spring 33 is prevented from moving the contact rod upwardly in opening direction. The downward force of the spring 33, which is somewhat stronger than the spring 39, on the end 25 of the lever 17, however, biases the lever 17 in a clockwise direction about the latch point 1921 thus applying a downward force to the contact rod 15 to provide contact pressure between the bridging contact 13 and the stationary contacts 11.

As the contacts burn or wear the downward force of the spring 33 moves the mass 37 downward thus maintaining contact pressure and compensating for contact burning or wearing.

The contacts are opened by energization of the trip device 23 which may be an electromagnet. Energization of the trip device 23 causes the latch 21 to disengage the latch end 19 of the lever 17 which releases the upward force of the spring 33. At the instant the lever 17 is unlatched the contact pressure becomes zero and the spring 33 starts the bridging contact 13 in opening direction. During the opening operation the lever 17 pivots about the pivot 27 which is held substantially stationary due to the inertia of the mass 37 and the upward force of the spring 39.

The stroke of the stored-energy device is such that the greatest acceleration of the bridging contact occurs during the period of the opening stroke when the arc is being drawn and then, due to the kinetic energy of the moving parts, moves the bridging contact to its fully open position. The mass 37 follows the opening move ment under the influence of the spring 39.

The lever system 15-17 enables the stored-energy device to act in two directions, that is, in closing direction to provide contact pressure and in opening direction to open the contacts. The arrangement is such that at the instant the lever 17 is released the contact pressure becomes zero and the force acting on the contacts will reverse its direction and start the movable contact in opening direction.

The contacts may be closed and the mechanism relatched by any suitable means such, for instance, as that shown in Figs. 2 and 5 which illustrate, by way of example, a practical embodiment of the invention.

Referring to Fig. 2, the circuit breaker includes a pair of spaced stationary contacts 41 and a cooperating movable bridging contact 43 mounted on the upper end of a contact rod 45. A stored-energy device indicated generally at 47 comprises a stack of spring washers 49 enclosed in a housing 51 and compressed between the bottom of the housing and a shoulder 53 on the contact rod 45. The rod 45 extends through an opening in the bottom of the spring housing 51 and is pivotally connected to a lever 55 at a point between the ends thereof by means of a pivot pin 57. One end of the lever 55 is pivotally connected to the spring housing 51 adjacent its lower end by a pivot pin 59 and the other end of the lever 55 is normally engaged by a latch 61 forming a part of a trip device shown generally at 63. T he spring housing 51 is supported on a mass 65 in the form of a lever (Fig. 3) pivotally mounted by means of a pivot pin 67 on a projection 69 integral with a breaker housing 71 which encloses and supports the breaker mechanisrn. The lever 65 is biased in an upwardly or clockwise direction by a spring 73 compressed between the housing 71 and the lever 65. Lateral movement of the contact rod 45 and the spring housing 51 is prevented by a link 75 having one end pivoted by a pin 77 to the spring housing 51 and the other end pivoted on a fixed point 79 on the breaker housing 71.

In the closed position of the breaker the springs 49 exert a downward force on the spring housing 51 and, through the pin 59, on the right end of the lever 55. Since the other end of the lever 55 is restrained by the latch 61 the downward force on the pin 59 biases the lever 55 in a downward or clockwise direction about the latch point. This downward force or bias is applied through the pin 57 to the rod 45 with a moment arm 57-59 to provide contact pressure in the closed position of the breaker.

Energization of the trip device 63 withdraws the latch 61 and releases the lever 55 thus releasing the spring 49 which results in the contact pressure immediately becoming zero. Since the spring housing 51 is supported by the mass 65 the spring 49 immediately moves the contact rod 45 upwardly at high speed to open the contacts. During the opening movement the lever 55 pivots about the pin 59 which is held substantially stationary by the inertia of the mass 65 and the upward force of the spring 39.

The stored-energy device 47 provides the greatest acceleration of the bridging contact during the first portion of the opening stroke when the arc is being drawn. Thereafter the kinetic energy of the moving parts moves the bridging contact to the fully open position. As shown in Fig. 4 the opening movement of the parts is stopped by the spring housing 51 striking the upper portion of the breaker housing 71. The mass 65 follows the opening movement of the spring housing 51 under the influence of the spring 73 to the position shown in Fig. 4 in dotted lines.

In order to prevent rebound of the parts from the open position and to hold them in the open position until the mass 65 completes its follow movement, a spring 81 is provided. This spring is tensioned between the lever 75 and the upper portion of the, breaker housing 71 and has just enough force to hold the movable parts of the breaker in the open position.

In order to close the circuit breaker it is necessary to retrieve and relatch the lever 55. This is accomplished by the operation of a bell crank 83 (Figs. 2 and 4) which is pivotally mounted by a pivot pin 85 in a bracket 87 supported on the base of the breaker housing 71. One arm 89 of the bell crank is pivotally connected to a link 91 which at its upper end carries a roller 93 for engaging the lever 55. The upper end of the link 91 is pivotally connected to one end of a lever 95 which has its other end pivoted on a fixed pivot 97 supported in the breaker housing 71. The other arm 99 of the bell crank 83 is pivotally connected to a piston rod 101 which at its other end is pivotally connected to a piston 103. The piston 103 is movable in a cylinder 105 and is biased by a spring 107 to the position shown in Fig. 2.

The closing operation is effected by admitting fluid under pressure to the cylinder 105 on the working side of the piston 103. Compressed fluid is admitted to the cylinder 105 through an inlet port 109 under the control of a suitable valve device (not shown). When compressed fluid is admitted to the cylinder 105 the piston 103 is driven toward the left rotating the bell crank 83 in a counterclockwise direction. This movement of the bell crank 83 draws the link 91 downwardly engaging the roller 93 with the lever 55 and moves this lever downwardly to reengage the left end thereof with the latch 61. At this time fluid is exhausted from the cylinder 105 under control of the valve device (not shown) and the spring 107 returns the piston 103 and bell crank 83 to the position shown in Fig. 2.

Means is provided to prevent complete closure of the contacts in the event the bell crank 83 fails to resume its normal position shown in Fig. 2 after completing its closing stroke. This means comprises a roller 111 (Figs. 2 and mounted on an arm 113 which is pivotally supported on a pivot pin 115 in a bracket 117 on the bottom portion of the breaker housing. The arm 113 together with the roller 111 is biased by a spring 119 in a counter- 4. clockwise direction, but is normally held in the position shown in Fig. 2 by a pin 121 on the arm 89 of the bell crank 83 engaging a projection 123 on the arm 113 in the closed position of the breaker.

When the bell crank is rotated by the piston 103 in a counterclockwise direction from its Fig. 2 position to close the breaker, the pin 121 frees the arm 113 and the spring 119 moves the arm 113 counterclockwise to position the roller 111 beneath the lower end of the contact rod 45. As the bell crank 83 continues its closing travel the lower end of the contact rod, just before the contacts touch, engages the roller 111 and is stopped thereby in the position shown in Fig. 5 while the bell crank 83 driven by the piston 10 3 completes its closing stroke. If the bell crank 33 fails to return to its normal position (Fig. 2) for any reason, for instance, failure to exhaust the fluid pressure from the cylinder 105, the roller 111 will remain under the contact rod 45 and hold the bridging contact 43 in the partially open position as shown in Fig. 5. As soon as the difficulty is corrected, the spring 107 will return the bell crank 33 to its normal position, the pin 121 kicking the roller 111 from under the contact rod 45 and permitting the stored-energy device to close the contacts.

In a normal closing operation the roller 111 serves as a rebound preventer since it reduces the closing speed just before the contacts touch.

The invention provides a high-speed circuit breaker in which a stored-energy device provides both the contact pressure and the force for opening the breaker. The arrangement is such that the contact pressure becomes Zero and the contacts start to open simultaneously the instant the circuit breaker is tripped. Means is provided to prevent the circuit breaker from being held in the closed position in the event of some failure in the device. This means prevents complete closure of the breaker in the event of some failure and on normal closing operations reduces the closing speed just before the contacts touch thereby preventing rebound of the moving contact.

Having described the invention in accordance with the provisions of the patent statutes, it is to be understood that various changes and modifications may be made in the structural details thereof without departing from the spirit of the invention.

We claim as our invention:

1. A high-speed circuit breaker having stationary and movable contact means, stored-energy means normally applying a force in a direction to open said contact means, a member on said stored-energy means causing said storedenergy means to apply a force in the opposite direction to provide contact pressure, trip means normally releasably restraining said member and operable to release said member, and said stored-energy means when said member is released instantaneously reducing said contact pressure to zero and simultaneously starting said movable contact means in opening direction.

2. A high-speed circuit breaker having stationary and movable contact means, stored-energy means applying a force to said movable contact in a direction to move said movable contact in opening direction, a lever mounted on said stored-energy device normally causing said stored energy device to apply a force to said movable contact in a direction to provide contact pressure, trip means normally engaging and releasably restraining said lever and said stored-energy means, said trip means being operable to release said lever, and said stored-energy means when said lever is released instantaneously reducing said contact pressure to zero and simultaneously starting said movable contact means in opening direction.

3. A high-speed circuit breaker having stationary and movable contact means, stored-energy means applying a force to said movable contact means in a direction to move said movable contact means in opening direction, a lever pivotally mounted on said stored-energy device and operatively connected to said movable contact means normally causing said stored-energy device to apply a force to said movable contact in a direction to provide contact pressure, trip means normally engaging and releasably restraining said lever and said stored-energy means, said trip means being operable to release said lever, and said stored-energy means when said lever is released instantaneously starting said movable contact means in opening direction.

4. A high-speed circuit breaker having stationary and movable contact means, a movable switch member having said movable contact means thereon, stored-energy means applying a force to said movable switch member in a direction to move said switch member in opening direction, a lever pivotally mounted on said stored-energy means and operatively connected to said movable switch member, trip means normally engaging and releasably restraining said stored-energy means in a position to cause said stored-energy means to apply a force to said movable switch member to thereby provide contact pressure, said trip means being operable to release said lever, and said stored-energy means when said lever is released instantaneously reducing said contact pressure to zero and simultaneously starting said movable switch member in opening direction.

5. A high-speed circuit breaker comprising stationary and movable contact means, a movable contact rod carrying said movable contact means, a stored-energy device for providing contact pressure and for moving said contact rod to open position, a lever having one end pivoted on said stored-energy device, said lever being pivotally connected to said movable contact rod, trip means normally engaging the other end of said lever and releasably restrainiing said stored-energy device, said stored-energy device when restrained applying a force to said movable contact rod to provide contact pressure, and said storedenergy device when said lever is released by operation of said trip means instantly starting said contact rod in opening direction to open said contact means.

6. A high-speed circuit breaker having stationary and movable contact means, stored-energy means applying a force in a direction to open said contact means, a biased mass supporting said stored-energy means, a member on said stored-energy means causing said stored-energy means to apply a force in the opposite direction to provide contact pressure, trip means normally releasably restraining said member and operable to release said member, and said stored-energy means when said member is released instantaneously starting said movable contact means in opening direction.

7. A high-speed circuit breaker having stationary and movable contact means, a movable switch member having said movable contact means thereon, stored-energy means applying a force to said movable switch member in a direction to move said switch member in opening direction, a biased mass supporting said stored-energy means, a lever pivotally mounted on said stored-energy means and operatively connected to said mavble switch member, trip means normally engaging and releasably restraining said stored-energy means in a position to cause said storedenergy means to apply a force to said movable switch member to thereby provide contact pressure, said trip means being operable to release said lever, and said stored energy means when said lever is released instantaneously reducing said contact pressure to zero and simultaneously starting said movable switch member in opening direction.

8. A high-speed circuit breaker comprising stationary and movable contact means, a movable switch member having the movable contact means thereon, stored-energy means applying a force to said movable switch member in a direction to move said switch member in opening direction, a lever having one end pivotally mounted on said stored-energy means and operatively connected to said movable switch member, trip means normally engaging the other end of said lever to releasably restrain said stored-energy means, said stored-energy means when restrained applying a force to said switch member to provide contact pressure, said trip means being operable to release said lever, said stored-energy means when said lever is released instantaneously starting said movable switch member in opening direction, closing means operable to move said switch member to the closed contact position, and blocking means preventing closing of said contact means until said closing means is restored to its operative position.

9. A high-speed circuit breaker comprising stationary and movable contact means, closing means operable to close said contact means, stored-energy means applying a force in a direction to open said contact means, a member on said stored-energy means operatively related to said movable contact means, trip means engaging and releasably restraining said member in a position to cause said stored-energy means to apply a force in the opposite direction thereby providing contact pressure, said trip means being operable to release said member, said storedenergy means when said member is released instantaneously moving said movable contact means in opening direction, and stop means positioned when said closing means is operated to close said contacts to be engaged by said movable contact means during the latter portion of the closing operation to prevent closing of said contact means until said closing means is restored to its operative position.

10. A high-speed circuit breaker having stationary and movable contact means, a movable contact rod carrying said movable contact means, a stored-energy device comprising spring means for providing contact pressure and for moving said contact rod to open position, a housing enclosing said spring means, a lever having one end pivotally mounted on said spring housing and operatively related to said contact rod, trip means normally engaging the other end of said lever to releasably restrain said stored-energy device, said stored-energy device when restrained applying a force to said movable contact rod to provide contact pressure, said stored-energy device when released by operation of said trip means instantantly reducing said contact pressure to zero and starting said contact rod in opening direction, and closing means for moving said contact rod to close said contact means and for storing energy in said stored-energy device.

11. In a high-speed circuit breaker having stationary and movable contact means, a lever operatively connected to said movable contact means, spring means compressed between said movable contact means and one end of said lever applying a force in a direction to move said movable contact means in opening direction, trip means releasably restraining the other end of said lever and operable to release said lever to permit said spring means to open said contact means, and a biased mass supporting said one end of said lever permitting said spring means in the restrained position of said lever to apply a force to said movable contact means in a direction to provide contact pressure.

12. A high-speed circuit breaker having stationary and movable contact means, a movable contact rod carrying said movable contact means on one end thereof, a lever pivoted on the other end of said contact rod, spring means compressed between said contact rod and one end of said lever biasing said contact rod in opening direction, latch means engaging the other end of said lever to releasably restrain said spring means, a movable mass supporting said one end of said lever, a spring biasing said mass against said one end of said lever permitting said spring means to bias said contact rod to closed position, and a trip device operable to effect release of said lever and opening of said contact means by said spring means.

References Cited in the file of this patent UNITED STATES PATENTS 1,626,769 Von Henke May 3, 1927 

